The chemical behaviour of molecules can be significantly modified by confinement to volumes comparable to the dimensions of the molecules. Although such confined spaces can be found in various nanostructured materials, such as zeolites, nanoporous organic frameworks and colloidal nanocrystal assemblies, the slow diffusion of molecules in and out of these materials has greatly hampered studying the effect of confinement on their physicochemical properties. Here, we show that this diffusion limitation can be overcome by reversibly creating and destroying confined environments by means of ultraviolet and visible light irradiation. We use colloidal nanocrystals functionalized with light-responsive ligands that readily self-assemble and trap various molecules from the surrounding bulk solution. Once trapped, these molecules can undergo chemical reactions with increased rates and with stereoselectivities significantly different from those in bulk solution. Illumination with visible light disassembles these nanoflasks, releasing the product in solution and thereby establishes a catalytic cycle. These dynamic nanoflasks can be useful for studying chemical reactivities in confined environments and for synthesizing molecules that are otherwise hard to achieve in bulk solution.

Rechargeable batteries paired with sodium (Na)-metal anodes are considered as one of the most promising high energy and low-cost energy storage systems. However, the use of highly reactive Na metal and the formation of Na dendrites during battery operation have caused signi cant safety concerns, especially when highly ammable liquid electrolytes are used. Herein, we design and develop a solventfree solid polymer electrolytes (SPEs) based on a per uoropolyether (PFPE) terminated polyethylene glycol (PEG)-based block copolymer for safe and stable all-solid-state Na-metal batteries. Compared with traditional poly(ethylene oxide) (PEO) or PEG SPEs, our results suggest that block copolymer design allows for the formation of self-assembled microstructures leading to high storage modulus at elevated temperatures with the PEG domains providing transport channels even at high salt concentration (EO/Na + = 8:2). Moreover, it is demonstrated that the incorporation of PFPE segments enhances the Na + transference number of the electrolyte to 0.46 at 80 o C. Finally, the proposed SPE exhibits highly stable symmetric cell cycling performance with high current density (0.5 mA cm -2 and 1.0 mAh cm -2 , up to 1300 hours). The assembled all-solid-state Na-metal batteries with Na 3 V 2 (PO 4 ) 3 cathode demonstrate outstanding rate performance, high capacity retention and long-term charge/discharge stability (CE = 99.91%) after more than 900 cycles.

To treat impairments in hard tissues or overcome pathological calcification in soft tissues, a detailed understanding of mineralization pathways of calcium phosphate materials is needed. Here, we report a detailed mechanistic study of hydroxyapatite (HA) mineralization pathways in an artificial saliva solution via in situ liquid cell transmission electron microscopy (TEM). It is found that the mineralization of HA starts by forming ion-rich and ion-poor solutions in the saliva solution, followed by coexistence of the classical and nonclassical nucleation processes. For the nonclassical path, amorphous calcium phosphate (ACP) functions as the substrate for HA nucleation on the ACP surface, while the classical path features direct HA nucleation from the solution. The growth of HA crystals on the surface of ACP is accompanied by the ACP dissolution process. The discoveries reported in this work are important to understand the physiological and pathological formation of HA minerals, as well as to engineer the biomineralization process for bone healing and hard tissue repairs.

Metal–organic frameworks (MOFs) are crystalline nanoporous materials with great potential for a wide range of industrial applications. Understanding the nucleation and early growth stages of these materials from a solution is critical for their design and synthesis. Despite their importance, the pathways through which MOFs nucleate are largely unknown. Using a combination of in situ liquid-phase and cryogenic transmission electron microscopy, we show that zeolitic imidazolate framework-8 MOF nanocrystals nucleate from precursor solution via three distinct steps: 1) liquid–liquid phase separation into solute-rich and solute-poor regions, followed by 2) direct condensation of the solute-rich region into an amorphous aggregate and 3) crystallization of the aggregate into a MOF. The three-step pathway for MOF nucleation shown here cannot be accounted for by conventional nucleation models and provides direct evidence for the nonclassical nucleation pathways in open-framework materials, suggesting that a solute-rich phase is a common precursor for crystallization from a solution.

Although dissipative self-assembly is ubiquitous in nature, where it gives rise to structures and functions critical to life, examples of artificial systems featuring this mode of self-assembly are rare. Here, we identify the presence of ephemeral assemblies during seeded growth of gold nanoparticles. In this process, hydrazine reduces Au(III) ions, which attach to the existing nanoparticles "seeds". The attachment is accompanied by a local increase in the concentration of a surfactant, which therefore forms a bilayer on nanoparticle surfaces, inducing their assembly. The resulting aggregates gradually disassemble as the surfactant concentration throughout the solution equilibrates. The lifetimes of the out-of-equilibrium aggregates depend on and can be controlled by the size of the constituent nanoparticles. We demonstrate the utility of our out-of-equilibrium aggregates to form transient reflective coatings on polar surfaces.

The development of new technologies for the removal of a family of manufactured chemicals, the per- and polyfluoroalkyl substances (PFAS), from the environment is urgently needed to safeguard public and environmental health. Here we report a fundamental study of the binding mechanisms driven by fluorine–fluorine and electrostatic interactions between perfluorooctanoic acid (PFOA), an important PFAS molecule, and three types of block copolymer sorbents containing individually perfluoropolyether (PFPE) or quaternized ammonium groups, or both functional segments in combination. The results show that both the fluorine–fluorine interactions between the PFPE segment of the block copolymer and the fluorinated tail of the PFOA as well as electrostatic attraction between the quaternized ammonium group and the anionic PFOA headgroup are crucial to achieve effective PFOA sorption from aqueous solutions. The fluorine–fluorine interactions contribute to recognition of PFOA molecules via fluorophilicity, with fast exchange between bound and free PFOA being observed, while the electrostatic interactions can tightly bind PFOA, thus precluding such exchange. Both types of interaction are observed to be rapidly established within 5 min. We show that the sorbents containing both fluorinated and cationic groups have a higher PFOA removal efficiency with potentially improved sorption capacity compared with the sorbents with a single functional group and that the electrostatic attraction is stronger and dominates the fluorine–fluorine interactions when the sorbent is highly charged. Overall, these results provide important insights into designing novel sorbents for rapid and efficient PFAS removal from contaminated environments.

Understanding how the spatial ordering of liquid crystalline nanoparticles can be controlled by different factors is of great importance in the further development of their photonic applications. In this paper, we report a new key parameter to control the mesogenic behavior of gold nanoparticles modified by rodlike thiols. An efficient method to control the spatial arrangement of hybrid nanoparticles in a condensed state is developed by changing the composition of the mesogenic grafting layer on the surface of the nanoparticles. The composition can be tuned by different conditions of the ligand exchange reaction. The thermal and optical behavior of the mesogenic and promesogenic ligands were investigated by using differential scanning calorimetry (DSC) and hot-stage polarized optical microscopy. The chemical structure of the synthesized hybrid nanoparticles was characterized by (1) H NMR spectroscopy, thermogravimetric analysis (TGA), XPS, and elemental analysis, whereas the superstructures were examined by small-angle X-ray diffraction (SAXSRD) analysis. Structural studies showed that the organic sublayer made of mesogenic ligands is denser with an increasing the average ligand number, thereby separating the nanoparticles in the liquid crystalline phases, which changes the parameters of these phases.

A major challenge in the preparation of polymeric 19 F magnetic resonance imaging (MRI) contrast agents (CAs) is signal attenuation caused by reduced segmental mobility of partly fluorinated polymers possessing large numbers of fluorine atoms. Previous studies have thus mainly focused on the development of fluorinated segments for improved 19 F MRI; however, detailed investigations of the role of hydrophilic segments on imaging performance remain scarce. In this study, three hydrophilic and biocompatible monomers, i.e., 2-(methylsulfinyl)ethyl acrylate (MSEA), oligo(ethylene glycol) methyl ether acrylate (OEGA), and oligo(2-methyl-2-oxazoline) acrylate (OMOXA), were used to prepare perfluoropolyether (PFPE)-containing amphiphilic block polymers through reversible addition−fragmentation chain-transfer (RAFT) polymerization. The effect of the different hydrophilic segments on 19 F imaging performance was explored. The three polymers could be readily dissolved in aqueous solutions, forming assemblies with the hydrophobic PFPE as the core and the hydrophilic chains as the shell. Molecular dynamics simulations demonstrate that the POMOXA chains adopt a rigid, extended conformation, leading to a relatively short 19 F NMR spin−spin relaxation time (T 2 ), lower NMR detectable 19 F spins (i.e., visibility), and the least intense 19 F MRI signal. In contrast, although PMSEA−PFPE has a shorter 19 F NMR T 2 than POEGA−PFPE, the much higher 19 F spin visibility enhances its MRI signal intensity. The result confirms the importance of maintaining both high fluorine visibility and long T 2 relaxation time to prepare effective CAs and highlight the key role of the nonfluorinated hydrophilic segments in determining these parameters.